38,606 research outputs found
Content Differences in Syntactic and Semantic Representations
Syntactic analysis plays an important role in semantic parsing, but the
nature of this role remains a topic of ongoing debate. The debate has been
constrained by the scarcity of empirical comparative studies between syntactic
and semantic schemes, which hinders the development of parsing methods informed
by the details of target schemes and constructions. We target this gap, and
take Universal Dependencies (UD) and UCCA as a test case. After abstracting
away from differences of convention or formalism, we find that most content
divergences can be ascribed to: (1) UCCA's distinction between a Scene and a
non-Scene; (2) UCCA's distinction between primary relations, secondary ones and
participants; (3) different treatment of multi-word expressions, and (4)
different treatment of inter-clause linkage. We further discuss the long tail
of cases where the two schemes take markedly different approaches. Finally, we
show that the proposed comparison methodology can be used for fine-grained
evaluation of UCCA parsing, highlighting both challenges and potential sources
for improvement. The substantial differences between the schemes suggest that
semantic parsers are likely to benefit downstream text understanding
applications beyond their syntactic counterparts.Comment: NAACL-HLT 2019 camera read
Thematic roles ā universal, particular, and idiosyncratic aspects
Thematic Roles (or Theta-Roles) are theoretical constructs that account for a variety of well known empirical facts, which are more or less clearly delimited. In other words, Theta-Roles are not directly observable, but they do have empirical content that is open to empirical observation. The objective of the present paper is to sketch the nature and content of Theta-Roles, distinguishing their universal foundation as part of the language faculty, their language particular realization, which depends on the conditions of individual languages, and idiosyncratic properties, determined by specific information of individual lexical items
Constraint-based computational semantics : a comparison between LTAG and LRS
This paper compares two approaches to computational semantics, namely semantic unification in Lexicalized Tree Adjoining Grammars (LTAG) and Lexical Resource Semantics (LRS) in HPSG. There are striking similarities between the frameworks that make them comparable in many respects. We will exemplify the differences and similarities by looking at several phenomena. We will show, first of all, that many intuitions about the mechanisms of semantic computations can be implemented in similar ways in both frameworks. Secondly, we will identify some aspects in which the frameworks intrinsically differ due to more general differences between the approaches to formal grammar adopted by LTAG and HPSG
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